Merge branch 'master' of flubber:~hurd-web/hurd-web

6 files changed, 25 insertions, 150 deletions

diff --git a/open_issues/libpthread_pthread_key_create_reuse.mdwn b/open_issues/libpthread_pthread_key_create_reuse.mdwn
deleted file mode 100644
index ca2da2f5..00000000
--- a/open_issues/libpthread_pthread_key_create_reuse.mdwn
+++ /dev/null
@@ -1,82 +0,0 @@
-[[!meta copyright="Copyright © 2011 Free Software Foundation, Inc."]]
-
-[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
-id="license" text="Permission is granted to copy, distribute and/or modify this
-document under the terms of the GNU Free Documentation License, Version 1.2 or
-any later version published by the Free Software Foundation; with no Invariant
-Sections, no Front-Cover Texts, and no Back-Cover Texts.  A copy of the license
-is included in the section entitled [[GNU Free Documentation
-License|/fdl]]."]]"""]]
-
-[[!meta title="libpthread: pthread_key_create, reuse"]]
-
-[[!tag open_issue_libpthread]]
-
-IRC, FreeNode, #hurd, 2011-07-02:
-
-    < pinotree> hm, maybe i found a libpthread bug
-    * pinotree tries a testcase
-    < pinotree> yesssss, found the bug :)
-    < pinotree> youpi: it's a problem of the key reuse in pthread_key_create()
-    < youpi> it doesn't reset it?
-    < youpi> were you looking at the licq issue?
-    < pinotree> no, gtest
-    < youpi> k
-    < youpi> licq has a failing threadspecific issue
-    < youpi> [  FAILED  ] ThreadSpecificData.dataDeletedWhenThreadExits
-    < pinotree> basically, pthread_key_delete() does not delete the key values
-      from the "thread_specifics" ihash
-    < pinotree> but those were new keys, so i'm not sure it is allowed to
-      return values of previous keys?
-    < pinotree> after all, the actual key value is an implementation detail,
-      applications shouldn't care about it being reused
-    < pinotree> (imho)
-    < youpi> Upon key creation, the value NULL shall be associated with the new
-      key in all active threads.
-    < youpi> ok, so we have to clear it in all threads
-    < youpi> that's a pity
-    < pinotree> or just remove the entry from the hash on key removal
-    < youpi> pinotree: from all the hashes, you mean?
-    < pinotree> youpi: from how i see it, adding a snippet like
-      http://paste.debian.net/121690/ in pthread_key_delete() should do the job
-    < youpi> that only drops from the current thread
-    < pinotree> ah hm, other threads
-    < youpi> we need to drop from all  threads
-    < youpi> that's the pity part
-    < pinotree> youpi: the licq case could look like a similar issue, at a
-      veeery quick glance
-
-Test program: [[pthread_key_create_reuse.c]]
-
-
-2011-11-01:
-
-    <pinotree> youpi: about the bug with pthread keys (reuse): would be an
-      acceptable solution having a mutex for the thread_specifics of each
-      thread?
-    <youpi> you mean one per thread, one global, or one per key, or ?
-    <youpi> what is it supposed to protect?
-    <pinotree> the thread_specifics of each thread
-    <youpi> pinotree: but against what?
-    <pinotree> the idea would be: when destroying a key, iterate over all the
-      exiting threads and remove the key data from the thread_specifics of each
-      thread
-    <youpi> one of the issue is getting to browse through the whole list of
-      threads
-    <youpi> the other is concurrency between that, and a thread dying
-    <pinotree> there's the __pthread_threads_lock rwlock
-    <youpi> it should be enough to keep it locked during the iteration
-    <pinotree> but that wouldn't be enough when one thread is destroying a key,
-      and another one is doing {get,set}specific() on that key
-    <youpi> that's not supposed to happen
-    <pinotree> mmm
-    <youpi> “The effect of calling pthread_getspecific() or
-      pthread_setspecific() with a     key value not obtained from
-      pthread_key_create() or after key has been     deleted with
-      pthread_key_delete() is undefined.”
-    <youpi> undefined -> you are allowed to just blow up
-    <pinotree> but it's not been deleted yet... :)
-    <youpi> it could be, just a matter of time
-    <youpi> you're not supposed to rely on time-luckyness :)
-    <pinotree> mmm
-    <pinotree> bah, you've convinced me ( :) )
diff --git a/open_issues/libpthread_pthread_key_create_reuse/pthread_key_create_reuse.c b/open_issues/libpthread_pthread_key_create_reuse/pthread_key_create_reuse.c
deleted file mode 100644
index f7f5874e..00000000
--- a/open_issues/libpthread_pthread_key_create_reuse/pthread_key_create_reuse.c
+++ /dev/null
@@ -1,48 +0,0 @@
-#include <pthread.h>
-#include <stdio.h>
-#include <assert.h>
-
-#define DEBUG
-
-void del(void *x __attribute__((unused)))
-{
-}
-
-void work(int val)
-{
-  pthread_key_t key1;
-  pthread_key_t key2;
-
-#ifdef DEBUG
-  printf("work/%d: start\n", val);
-#endif
-  assert(pthread_key_create(&key1, &del) == 0);
-  assert(pthread_key_create(&key2, &del) == 0);
-#ifdef DEBUG
-  printf("work/%d: pre-setspecific: %p,%p\n", val, pthread_getspecific(key1), pthread_getspecific(key2));
-#else
-  assert(pthread_getspecific(key1) == NULL);
-  assert(pthread_getspecific(key2) == NULL);
-#endif
-  assert(pthread_setspecific(key1, (void *)(0x100 + val)) == 0);
-  assert(pthread_setspecific(key2, (void *)(0x200 + val)) == 0);
-#ifdef DEBUG
-  printf("work/%d: post-setspecific: %p,%p\n", val, pthread_getspecific(key1), pthread_getspecific(key2));
-#else
-  assert(pthread_getspecific(key1) == (void *)(0x100 + val));
-  assert(pthread_getspecific(key2) == (void *)(0x200 + val));
-#endif
-  assert(pthread_key_delete(key1) == 0);
-  assert(pthread_key_delete(key2) == 0);
-}
-
-int main()
-{
-  int i;
-
-  for (i = 0; i < 8; ++i) {
-    work(i + 1);
-  }
-
-  return 0;
-}
diff --git a/open_issues/performance/io_system/binutils_ld_64ksec.mdwn b/open_issues/performance/io_system/binutils_ld_64ksec.mdwn
index d0b8ea7f..931fd0ee 100644
--- a/open_issues/performance/io_system/binutils_ld_64ksec.mdwn
+++ b/open_issues/performance/io_system/binutils_ld_64ksec.mdwn
@@ -27,10 +27,6 @@ extracted from cdf7c161ebd4a934c9e705d33f5247fd52975612 sources, 2010-10-24.
 On the idle grubber, this one repeatedly takes a few minutes wall time to
 complete successfully, contrary to a few seconds on a GNU/Linux system.
 
-> On order of slowness may in fact be due to a Xen-specific issue, see
-> [[xen_lseek]].  (But there are probably still one or two orders left, even
-> without Xen.)
-
 While processing the object files, there is heavy interaction with the relevant
 [[hurd/translator/ext2fs]] process.  Running [[hurd/debugging/rpctrace]] on
 the testee shows that (primarily) an ever-repeating series of `io_seek` and
@@ -38,19 +34,6 @@ the testee shows that (primarily) an ever-repeating series of `io_seek` and
 shows the equivalent thing (`_llseek`, `read`) -- but Linux' I/O system isn't
 as slow as the Hurd's.
 
----
-
-IRC, freenode, #hurd, 2011-09-01:
-
-    <youpi> hum, f951 does myriads of   71->io_seek_request (32768 0) = 0 32768
-    <youpi> no wonder it's slow
-    <youpi> unfortunately that's also what it does on linux, the system call is
-      just less costly
-    <youpi> apparently gfortran calls io_seek for, like, every token of the
-      sourced file
-    <youpi> (fgetpos actually, but that's the same)
-    <youpi> and it is indeed about 10 times slower under Xen for some reason
-
-Also see testcase [[test-lseek.c]] and [[test-mach.c]]
-
-[[!tag open_issue_xen]]
+As Samuel figured out later, this slowness may in fact be due to a Xen-specific
+issue, see [[Xen_lseek]].  After the latter has been addressed, we can
+re-evaluate this issue here.
diff --git a/open_issues/xen_lseek.mdwn b/open_issues/xen_lseek.mdwn
index accc7c8f..756abf5e 100644
--- a/open_issues/xen_lseek.mdwn
+++ b/open_issues/xen_lseek.mdwn
@@ -10,6 +10,17 @@ License|/fdl]]."]]"""]]
 
 [[!tag open_issue_xen]]
 
+IRC, freenode, #hurd, 2011-09-01:
+
+    <youpi> hum, f951 does myriads of   71->io_seek_request (32768 0) = 0 32768
+    <youpi> no wonder it's slow
+    <youpi> unfortunately that's also what it does on linux, the system call is
+      just less costly
+    <youpi> apparently gfortran calls io_seek for, like, every token of the
+      sourced file
+    <youpi> (fgetpos actually, but that's the same)
+    <youpi> and it is indeed about 10 times slower under Xen for some reason
+
 IRC, freenode, #hurd, 2011-11-02:
 
     <youpi> btw, we have a performance issue with xen
@@ -33,3 +44,14 @@ IRC, freenode, #hurd, 2011-11-02:
       http://www.gnu.org/software/hurd/open_issues/performance/io_system/binutils_ld_64ksec.html
 
 [[performance/io_system/binutils_ld_64ksec]].
+
+Also see the simple testcases [[test-lseek.c]] and [[test-mach.c]].
+
+IRC, freenode, #hurd, 2011-11-05:
+
+    <youpi> [test-mach.c is] mostly as a reference for the trap overhead
+    <youpi> 0.56µs (xen) vs 0.48µs(kvm) on test-mach
+    <youpi> 455µs(xen) vs 16µs(kvm) on test-lseek
+    <youpi> that might simply be an issue in the RPC  mechanism, which behaves
+      badly with the xen memory management
+    <youpi> yes, about 0.5ms for an lseek, that's quite high :)
diff --git a/open_issues/performance/io_system/test-lseek.c b/open_issues/xen_lseek/test-lseek.c
index 667dce66..667dce66 100644
--- a/open_issues/performance/io_system/test-lseek.c
+++ b/open_issues/xen_lseek/test-lseek.c
diff --git a/open_issues/performance/io_system/test-mach.c b/open_issues/xen_lseek/test-mach.c
index 90337346..90337346 100644
--- a/open_issues/performance/io_system/test-mach.c
+++ b/open_issues/xen_lseek/test-mach.c